ENVO WH-AZ54-199-LPO vs LOCHINVAR ATO-199B-N 1**: which uses less energy?
At the high draw pattern the ENVO WH-AZ54-199-LPO uses 195 therms a year and the LOCHINVAR ATO-199B-N 1** 206 — 12 therms (6%) less, about 119 therms over ten years. Both are filed as a gas tankless unit, so the comparison holds. Enter your ZIP below to price the difference.
Side by side
Compared within one class only: models filed as a gas tankless unit at the high draw pattern.
| Figure | ENVO WH-AZ54-199-LPO | LOCHINVAR ATO-199B-N 1** |
|---|---|---|
| UEF (Uniform Energy Factor) | 0.87 (better) | 0.82 |
| Energy use per year (therms) | 195 (better) | 206 |
| Max flow (GPM) | 5 | 5 |
| Installed cost range | $1,981–$2,963 | $1,745–$2,687 |
| ENERGY STAR certified | not matched | not matched |
What it costs to run
Reliability
Not published: Reliability, failure rates and each model’s actual warranty term.
The registries these figures come from certify energy performance under a federal test; none of them records how long a unit lasts or how often it fails, so this page does not rank the two on reliability.
What is here instead:
- The filed efficiency, capacity and tank size of both models, side by side below.
- The actual warranty term is printed in each model’s documentation, not in any registry.
Which should you pick?
- Pick the ENVO WH-AZ54-199-LPO if running cost matters most: it uses 12 therms less a year on the same test.
- Pick the LOCHINVAR ATO-199B-N 1** if the installed price matters more than the running cost: its modeled installed range is $1,745–$2,687 against $1,981–$2,963.
- Neither if you need more than 5 GPM at the same time — neither unit lists more. Check how to size a tankless unit by GPM.
Each model on its own
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ENVO WH-AZ54-199-LPO
Its filed figures, class position and running cost on your ZIP.
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LOCHINVAR ATO-199B-N 1**
Its filed figures, class position and running cost on your ZIP.